Bias current generating circuits and methods are widely used in integrated circuits in order to generate a bias current for the integrated circuit, from an external power supply voltage. For example, field effect transistors such as Metal Oxide Semiconductor (MOS) transistors in an integrated circuit may be controlled by bias currents that are provided by a bias circuit.
In order to provide a controlled amount of bias current, it is desirable for the bias current to remain uniform, notwithstanding changes in the external power supply voltage, changes in temperature and/or integrated circuit fabrication process variations. Moreover, for high-speed integrated circuit devices such as high-speed integrated circuit memory devices, it is desirable for the bias current to rapidly reach a desired level when the integrated circuit transitions from a power-down state to a standby state or an active state. If excessive time is taken to generate the bias current, the operational speed of the integrated circuit may decrease and/or a malfunction may occur.